Martin Logan CLSIIz - adding more bass?

i'd suggest a pair of subs crossed over @ 60-70hz, w/a min of 24db/octave slope. i'd also suggest a pair of vmps larger subs. these are *awfully* hard to find used, but even brand-new, there's nothing that approaches 'em at anywhere near the price, even used. plus, their price includes direct shipping. most dealers will discount these at least 15%. pair these w/a decent x-over from db systems or marchand (or some hi-end used x-over), & a good used solid-state amp, & yule be happy. mebbe it'll be a bit more than $1500, but not by much, and at least yule be happy w/the results. i also buy mostly used, but the vmps were a no-brainer, & i've no desire to change (except to upgrade to their most recent drivers, but it's hard to imagine they could be faster/tighter than what i already have!)

i'd suggest a pair of subs crossed over @ 60-70hz, w/a min of 24db/octave slope. i'd also suggest a pair of vmps larger subs. these are *awfully* hard to find used, but even brand-new, there's nothing that approaches 'em at anywhere near the price, even used. plus, their price includes direct shipping. most dealers will discount these at least 15%. pair these w/a decent x-over from db systems or marchand (or some hi-end used x-over), & a good used solid-state amp, & yule be happy. mebbe it'll be a bit more than $1500, but not by much, and at least yule be happy w/the results. i also buy mostly used, but the vmps were a no-brainer, & i've no desire to change (except to upgrade to their most recent drivers, but it's hard to imagine they could be faster/tighter than what i already have!)

What about the REL Stadium? Most CLS owners I've corresponded with claim this is the sub to have.

Thanks for everyone's responses...what about the crossover. Should I used an electronic one or a passive one?